Journal#1: The human body contains trillions of cells, how many different types do you think

there are?

• Fun Fact: The human heart creates enough pressure to squirt blood 30 feet in the air.

• Objective:– List the 4 major tissue

types in the body– Discuss the types and

functions of epithelial cells

Epithelial Tissue

Pgs. 107-118

Intro to Tissues

• Combinations of specialized cells that work together to perform a function

• The study is called Histology

• Four Basic Tissue Types– Epithelial– Connective– Muscle– Neural

Epithelial Tissue

• Includes :– Epithelia: Layers of cells that cover internal & external

surfaces– Glands: Structures that make fluid secretions and are

attached to or derived from the epithelia• Characteristics

– Cellularity: cells bound by cell junctions– Polarity: has an exposed & attached surface– Attachment: the base is bound to a thin basal lamina

with connective tissue below– Avascularity: no blood vessels– Regeneration: Replaced by stem cells in the

epithelium (high mitotic rate)

Functions of Epithelial Tissue

• Protection: from abrasion, dehydration, and destruction

• Control permeability: create a semi permeable barrier

• Provide Sensation: sensory receptors (skin)

• Produce Secretions: gland cells produce enzymatic fluids, hormones, etc.

Specialization

• Move fluids over surface

• Move fluids through the epithelium

• Produce Secretions

• Specialized Structures– Microvilli (increase surface area for absorption

and secretions)– Ciliated epithelium (beat cilia to move fluids

across cell)

Intercellular Connections

• Epithelial Cells firmly attached to each other• Also attached to basal lamina

– Where stem cells or germinative cells are located • Adjacent cells connected by proteins called cell

adhesion molecules (CAMs)• Types of cell junctions (connections)

– Tight: lipid portion of membrane joined by interlocking proteins (adhesion belt)

• Prevent diffusion between cells– Gap: held together by interlocking proteins

• Allows diffusion between cells– Desmosome: attach cells to extracellular structures

like the basal lamina

Journal#2: What are the 3 types of cell junctions or connections in epithelial tissue?

• Fun Fact:

Feet have 500,000 sweat glands and can produce more than a pint of sweat a day.

• Objective:– List the 4 major tissue

types in the body– Discuss the types and

functions of epithelial cells

Classification of Epithelium

• Cell shape:– Squamous: thin and flat– Cuboidal: little boxes– Columnar: tall and slender

• Layers:– Simple: 1– Stratified: more than one

Squamous

• Simple– Delicate– Diffusion ready– Blood vessels, tubules

of kidneys, lining of cornea, mesothelium (lining of body cavities)

• Stratified– Protection– Skin, lining of mouth,

throat, esophagus

Cuboidal

• Simple– Limited protection– Absorption/Secretion– Kidney Tubules,

Glands, Ducts

• Stratified (rare)– Protection– Absorption/Secretion– Ducts of sweat glands

Transitional

• Tolerates stretching without damage

• Urinary bladder– Empty: seems to be

layered w/cuboidal on surface

– Full: appears flattened like simple squamous

Columnar

• Simple– Absorption/secretion– Lining of stomach &

intestines

• Pseudostratified ciliated– Protection/secretion– Nasal cavity, trachea, &

bronchi

• Stratified (rare)– Protection– Pharynx, epiglottis, anus, &

urethra

Glandular

• Endocrine Glands– Release fluids (hormones) into interstitial fluid– Directly to bloodstream

• Exocrine Glands– Release fluids on to epithelial surface– Skin/sweat, tears in eyes, milk by mammary

glands

Modes of Secretion• Merocrine

– Exocytosis of secretory vesicle– Perspiration, mucus

• Apocrine– Loss of cytoplasm becomes secretion– Milk production

• Holocrine– Lysis releases secretory products– Sebaceous glands (hair follicles)

Types of Secretions

• Serous glands– Watery solution (saliva)

• Mucous glands– mucous

• Mixed Exocrine glands– both

Gland Structure

• Unicellular (goblet cells)

• Multicellular– Secretory sheet– Simple: single duct– Compound: duct divides many times